Isotopic evidence in tree rings for historical changes in atmospheric sulfur sources

Little is understood about the usefulness of sulfur isotopic ratios (sigma 34S) in tree rings because the sulfur content in rings is generally insufficient for analysis using conventional methods. We present sigma 34S values of the water-soluble and the organically bound sulfur fractions in rings of coniferous trees grown in Japan, analyzed using a large-volume oxygen bomb. Comparing the sigma 34S values of the organically bound fraction in tree rings with past atmospheric sulfur concentrations and with those of their sources, we find clear evidence that the sigma 34S values of the organically bound fraction in the rings are dependent upon the values of the atmospheric sulfur sources. The evidence suggests that the sigma 34S values in tree rings are a useful chronological proxy for evaluating possible causes of past atmospheric sulfur pollution.     

In-process measurement of topography change of grinding wheel by using hydrodynamic pressure

This paper deals with an in-process measurement method for topography change of a grinding wheel, which can apply to wet grinding. A pressure sensor is set beside a grinding wheel with a small gap. When grinding fluid is dragged into the gap, hydrodynamic pressure, which corresponds to the gap length and the topography, can be measured. This method is applied to a cylindrical grinding machine. No electromagnetic properties of a workpiece and a grinding wheel affect measured results. The pressure is decreased with the increase of the gap length when the grinding fluid is supplied in the tangential direction of the grinding wheel. Spectra of the pressure are measured with an FFT analyzer. Higher frequency components are increased with the progress of grinding because of turbulent flow. Loading and dulling of a grinding wheel can be detected by the proposed method as well as its wear.     

Residual stress evaluation in resin-molded IC chips using finite element analysis and piezoresistive gauges

The high residual stress in a resin-molded electronic package sometimes makes the electronic functions unstable. Therefore the residual stress in electronic packages, especially on the top surfaces of semiconductor chips, should be evaluated. The objective of this study is to present a simple method for evaluating residual stress in resin-molded semiconductor chips using a combination of experimental and numerical methods. The actual residual stress of the packaging process was measured by using test chips that included piezoresistive gauges. A linear thermoelastic finite element analysis was then carried out using a three-dimensional model. The finite element analysis was performed under a stress-free temperature determined by the temperature dependence of the residual stress, which was experimentally measured by using the piezoresistive test chips. The measured residual stress using the test chips agreed well with the results of the finite element analysis. It was therefore confirmed that the present evaluation method, combining experimental and numerical methods, is reliable and reasonable.     

Numerical Characterization of Dosimetry,Human Body Resistance and Heart Current Resulting from Power-Frequency Touch Current for an Anatomically Realistic Human Model

Characteristics of power-frequency touch current inside an anatomically realistic human model of Japanese adult were numerically analyzed under various scenarios of current paths using a modified scalar potential finite difference (SPFD) method. Then, complex distributions of the current density in the model were visually illustrated. Results of the dosimetry of current density for excitable tissues indicates that the touch current within the reference level (0.5 mA) does not always satisfy the basic restriction of current density in the light of ICNIRP guideline for general public. Two sets of the internal body resistances R_i (i.e., 1130–1510Ω and 1460–1920Ω) are obtained, depending on the conductivity sets used. Although R_i considerably depends on the current scenario concerned, the highest values of Ri were obtained for the hand-to-hand scenario, regardless of the conductivity set. The inhomogeneous model always gives a higher value of R_i than does the homogeneous model that has a single conductivity equivalent to the weighted-average conductivity of the inhomogeneous model. It is found that the conductivity of muscle has significant influence on R_i, and that the resistance around the wrist and ankle is one of the predominant parameters to decide R_i. It is clearly shown that the current scenarios affect the pattern of the heart current flow, especially the direction of it, to a large extent. It is found that a current of 34–40% of touch current flows into the heart, and then the heart-current ratio is remarkably larger than old data. The heart-current factors of around 0.85 obtained are almost independent of the current scenarios, unlike those indicated in IEC60479-1, provided that the direction of heart current is ignored. © 2009 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Identification of HLA-A24-restricted epitopes with high affinities to Hsp70 using peptide arrays

Heat shock protein 70 (Hsp70) family members are known as facilitators of immune responses by interacting with receptors on antigen-presenting cells leading to Hsp70-peptide uptake and antigen cross priming. Here, identification of human leukocyte antigen (HLA)-A24-restricted epitopes was achieved using peptide arrays for evaluation of their affinities to Hsp70 and HLA-A24 binding prediction tools. Using Hsp70 as the model antigen, the GYPVTNAVI and VFQHGKVEI peptides were identified as antigens. These peptides actually bound to HLA-A24 in the stabilization assay using T2-A*2402 cells, and induced a strong peptide-reactive cytotoxic T lymphocyte response in HLA-A24 transgenic mice after vaccination.     

Kinetically Stable Bicelles with Dilution Tolerance,Size Tunability,and Thermoresponsiveness for Drug Delivery Applications

Mixtures of a phospholipid (1,2‐dipalmitoyl‐sn‐glycero‐3‐phosphatidylcholine, DPPC) and a sodium‐cholate‐derived surfactant (SC‐C₅) at room temperature formed phospholipid bilayer fragments that were edge‐stabilized by SC‐C₅: so‐called “bicelles”. Because the bilayer melting point of DPPC (41 °C) is above room temperature and because SC‐C₅ has an exceptionally low critical micelle concentration (<0.5 mm ), the bicelles are kinetically frozen at room temperature. Consequently, they exist even when the mixture is diluted to a concentration of 0.04 wt %. In addition, the lateral size of the bicelles can be fine‐tuned by altering the molar ratio of DPPC to SC‐C₅. On heating to ≈37 °C, the bicelles transformed into micelles composed of DPPC and SC‐C₅. By taking advantage of the dilution tolerance, size tunability, and thermoresponsiveness, we demonstrated in vitro drug delivery based on use of the bicelles as carriers, which suggests their potential utility in transdermal drug delivery.     

Relationship between degree of polymerization and optical and thermal properties of fluorene in polycarbonate polymers

The influences of average degree of polymerization (D_p) and terminal group on thermal and optical properties of high refractive indexed transparent polymers were investigated. In this study, 9,9‐bis[4–(2‐hydroxyethoxy) phenyl] fluorene (BPEF) homo polymer was selected because it has been used as a representative monomer in high refractive index polymers as well as its unique property. BPEF has stable amorphous phase and reacts like a polymer. Its unique reaction allows continuous investigation from monomer to polymer. For hydroxyl‐terminated polymer, the refractive index (n_d) decreased with increasing D_p. On the other hand, for a phenolic‐terminated group, n_d increased with increasing D_p, and both converged to same value in high D_p region. As for glass transition temperatures (T_g), both terminal group series were increased as D_p increased. Though T_g of hydroxyl‐terminated polymer was higher than that of phenolic‐terminated polymer in the low D_p region, both converged to the same value and the inverse number of T_g had linear correlation against the weight percentage of carbonyl groups (CO), which was calculated by D_p. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2017 , 134, 45042.     

Effect of micro gravity on the product selectivity of dichlorodifluoromethane electrolysis at metal supported gas diffusion electrodes

The micro gravity effect on the product selectivity of electrochemical reduction of CCl₂ F₂ (CFC-12) was studied using the metal supported gas diffusion electrodes (GDEs). Under the micro gravity, the current efficiency for methane formation (the final product) increased, whereas that for CHClF₂formation (a intermediate product) decreased at the Cu-supported GDE compared with the result under the normal gravity. This result suggests that the convection has an influence on the product selectivity for electrochemical reaction.     

有机朗肯循环的研究进展

有机朗肯循环是一种被认为能有效利用低温热能的技术。科研工作者在不同方面（包括工质、膨胀机、换热器的影响、系统的优化）对有机朗肯循环系统效率的影响进行了大量的研究。本文针对不同热源的工质筛选、膨胀机的特点、系统循环优化以及换热器的影响方面进行了讨论和总结,为有机朗肯循环系统的实际应用提供参考。